And does that anything else than maybe show racial fllags on the map or so?Say, will NPRs try to go closer/not go closer depending on their traits and me being in neutral/my system? I guess some aggressive NPRs may be angered by me building so big flag pole ..and so they arrive faster.

Yes agree claims would be nice.The only effect I have seen it have is on what info is displayed on the galaxy map, depending on your settings it may not show you how many unsurveyed bodies/JP:s you have in a system you set as owned by another race.